Gas generator for air bag and air bag device

ABSTRACT

The present invention provides a gas generator in which ignition and combustion performance of a gas generating agent and operation performance are enhanced. An inner cylindrical member  4  is disposed in a cylindrical housing  3 , an annular first combustion chamber  5   a  is provided radially in the outside of the inner cylindrical member  4 , and, in the combustion chamber  5   a , a ratio (D/L) of its radial average distance (D) to its axial average length (L) is adjusted to be in the range of 0.2 to 2.0. The invention provides a gas generator for an air bag capable of reducing a size of the gas generator and easily and reliably adjusting a capacity of a combustion chamber which accommodates the gas generating agent, and also provides a retainer for such a gas generator. The invention provides a retainer which changes a flow of a gas ejected from a through-hole of an inner cylindrical member provided in the housing and has a cylindrical portion for collecting fluid and semifluid combustion products included in the gas, and provides a gas generator for an air bag using such a retainer. The invention provides a gas generator for an air bag comprising, in a housing having a gas discharging port, a inner cylindrical member having a cylindrical peripheral wall, and two combustion chambers defined by the inner cylindrical member, in which a gas generating agent to be ignited for generating a working gas is charged in the respective combustion chambers, and working gases generated in the respective combustion chambers pass through different flow-paths and reach the gas discharging port. The present invention further provides a gas generator for an air bag in which, in a housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall is disposed, two combustion chambers are defined by the inner cylindrical member, a gas generating agent which is burnt to generate a working gas is charged in each of the combustion chambers, and working gases generated in the respective combustion chambers pass through different flow-paths to reach a coolant means.

DESCRIPTION GAS GENERATOR FOR AIR BAG AND AIR BAG APPARATUS

[0001] 1. Technical Field where the Invention Belongs

[0002] The present invention relates to a gas generator for an air bag disposed in a vehicle and preferably used for the air bag to protect a passenger from an impact, and to an air bag apparatus using the gas generator.

[0003] 2. Prior Art

[0004] An air bag apparatus is mounted in an automobile and the like to protect a passenger from an impact at the time of collision. The air bag apparatus is formed such as to rapidly generate gas by actuation of a gas generator for an air bag, thereby expanding the air bag (bag body).

[0005] Generally in a gas generator, when an ignition means is actuated by the impact, a gas generating agent is ignited and burnt to generate a high temperature and high pressure gas, and the generated gas ejected from a gas discharging port into the air bag (bag body).

[0006] Conventionally, the ignition means only comprises an igniter which is actuated by the actuating signal, or comprises a combination of the igniter and an transfer charge to be ignited and burnt by the actuated igniter.

[0007] A combustion chamber in which the gas generating agent is accommodated is variously designed depending upon a shape of a housing, a layout of necessary constituent members and the like, and as to the gas generating agents charged therein, there are various shapes and compositions.

[0008] Combustion degree of the gas generating agent is an important design factor for adjusting the operation performance of the gas generator. Therefore, it is preferable that the gas generating agent charged in the combustion chamber is effectively and reliably ignited and burnt by the actuation of the ignition means.

[0009] However, the conventional gas generator is still susceptible to improvement for enhancing the ignition performance of the gas generating agent.

[0010] An amount of the gas generating agent used in the gas generator is also an important factor for adjusting the operation performance of the gas generator. Usually, the gas generating agent is charged in the combustion chamber provided in the housing, so that it is necessary to adjust the capacity of the combustion chamber in order to adjust the amount of gas generating agent.

[0011] Further, conventionally, there is a gas generator in which two combustion chambers are provided in the housing, and the gas generating agent is charged in each of the combustion chambers. In order to obtain an optimal operation performance, the gas generator is formed such that igniting timing of the gas generating agent in each of the combustion chambers can be adjusted. In such a gas generator, it is preferable that the combustion of the gas generating agents accommodated in each combustion chamber can independently be adjusted, and it is necessary that the gas generator can easily be produced and a size thereof is reduced.

DISCLOSURE OF THE INVENTION

[0012] The present invention provides a gas generator in which ignition and combustion performance of the gas generating agent is enhanced by improving an inside structure of the gas generator, thereby enhancing the operation performance.

[0013] In a gas generator for an air bag of the present invention, by adjusting a shape of the combustion chamber in which the gas generating agent is accommodated and an ejecting position of a flame caused by actuation of the ignition means toward the combustion chamber, the ignition and combustion performance of the gas generating agent is enhanced and sufficient actuation output is obtained.

[0014] In other words, the present invention provides a gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member defining an inner space of the housing, an ignition means arranged inside the inner cylindrical member, an annular first combustion chamber for accommodating a gas generating agent provided radially outside the inner cylindrical member, wherein the first combustion chamber is adjusted such that a ratio (D/L) of the radial average distance (D) thereof to the axial average length (L) thereof is in the range of 0.2 to 2.0.

[0015] Here, the first combustion chamber is a space for accommodating the gas generating agent in the housing. The axial average length (L) of the first combustion chamber is an average length of the first combustion chamber in the axial direction of the housing. The radial average distance (D) of the first combustion chamber is an average distance of the first combustion chamber in the radial direction of the housing.

[0016] The inner cylindrical member is provided with a flame-transferring port for ejecting flames generated by actuation of the ignition means into the first combustion chamber. Also by controlling a position where the flame-transferring port is formed in a relation to the axial length of the first combustion chamber, the object of the invention can be achieved. More specifically, the object can also be achieved by a gas generator for an air bag in which the flame-transferring port is formed in the area (L₁/L≦¼) such that a distance L₁ from the center of the axial average length measured from the housing inner bottom surface in the first combustion chamber is not more than ¼ of the axial average length L in the first combustion chamber. When the housing comprises a diffuser shell in a cylindrical shape with a top having the gas discharging port and a closure shell in a cylindrical shape with a bottom forming the inner space together with the diffuser shell, the inner bottom surface of the housing corresponds to the inner bottom surface of the closure shell.

[0017] It is preferable that the flame-transferring port is positioned in the area such that a distance L₁ from the center of the axial average length measured from the housing inner bottom surface in the first combustion chamber is not more than ¼ of the axial average length L in the first combustion chamber.

[0018] According to the gas generator of the present invention, by adjusting the D/L to be in the range of 0.2 to 2.0 and further arranging L₁/L≦¼, flames of the ignition means to ignite the gas generating agent in the first gas generating chamber (first gas generating agent, hereinafter) is ejected toward the center of the axial direction in the first combustion chamber, so that the ignition and combustion performance of the first gas generating agent is enhanced. That is, by forming in the above manner, the flame of the ignition means ejected into the first combustion chamber spreads widely in the combustion chamber to ignite more amount of gas generating agents than other wise, so that the ignition and combustion performance of the first gas generating agent can be enhanced.

[0019] The present invention can be realized by a gas generator in which the inner cylindrical member is disposed in the housing, the ignition means is arranged inside the inner cylindrical member, the annular first combustion chamber is provided radially in the outside thereof and the flame of the ignition means disposed inside the inner cylindrical member passes through the flame-transferring port provided in the inner cylindrical member to be ejected into the first combustion chamber. Therefore, the present invention can be realized regardless of other structures such as whether two combustion chambers are defined in the housing, a layout thereof and the number of ignition means. The present invention can be also realized with a gas generator in which the combustion chamber accommodating the gas generating agent exists radially in the outside of the inner cylindrical member, but no other combustion chamber is provided inside the inner cylindrical member. In this case, the ignition means can be accommodated inside the inner cylindrical member.

[0020] In the present invention, the axial length of the first combustion chamber can be limited by an inner surface of the housing existing in the axial direction of the first combustion chamber. When the first combustion chamber is adjusted, a retainer having a partition wall surface can be disposed on an axial end of the first combustion chamber, and an axial end of the first combustion chamber can be defined by the partition wall surface. In other words, retainers can be disposed axially on the opposite sides of the first combustion chamber to limit the axial length of the combustion chamber, or a retainer can be disposed axially on one side of the combustion chamber to limit axial length of the combustion chamber with the housing and the retainer, or the axial length of the combustion chamber can be limited by an inner surface of the housing without disposing any retainer in the combustion chamber. In this case, the axial average length (L) of the first combustion chamber can be defined as an average distance between the retainers, an average distance between an inner surface of the housing and the retainer, or an average distance between inner surfaces of the housing. The retainer is demanded to define at least the axial length of the first combustion chamber and is provided with at least a partition wall surface in a shape to axially close the first combustion chamber. The retainer can also form a flow-path for allowing a working gas to pass the opposite side of the first combustion chamber, or can divide the coolant means, if required. For example, the first combustion chamber and the flow-path of the working gas can be partitioned by the partition wall surface.

[0021] Further, when the inner cylindrical member is disposed in the housing, an end of the inner cylindrical member is formed in a shape to close the first combustion chamber such as an outwardly directed flange-like shape and with this, the axial length of the first combustion chamber can be limited.

[0022] The radial distance of the first combustion chamber can be defined by the outer peripheral surface of the inner cylindrical member and a member arranged radially in the outside the first combustion chamber. In this case, the radial average distance (D) can be defined as an average distance between the outer peripheral surface of the inner cylindrical member and the member arranged radially in the outside of the first combustion chamber. As the member arranged radially in the outside of the first combustion chamber, for example, a coolant means or filter means for cooling and/or purifying the working gas generated by combustion of the gas generating agent can be used.

[0023] In the gas generator, the ignition performance of the first gas generating agent can be enhanced by a structure of the gas generator. Thus, even if the ignition performance of the first gas generating agent is slightly inferior, the first gas generating agent can be satisfyingly burnt. In other words, by controlling the shape of the first combustion chamber or an arrangement of a flame-transferring port, even the gas generating agent without a satisfying ignition performance can be used as the first gas generating agent. Improvement on the ignition performance of the gas generating agent can be measured, for example, by the time when the maximum pressure inside the gas generator at activation can obtained, or a tank curve (pressure time curve in 60-liter tank) obtained by the 60-liter tank test (tank combustion test).

[0024] The gas generator can constitute an air bag apparatus together with an impact sensor to detect the impact and actuate the gas generator, an air bag for introducing a gas generated in the gas generator to inflate and a module case for accommodating the air bag.

[0025] The gas generator is accommodated in the module case together with the air bag (bag body) for introducing a generated gas to inflate and is provided as a pad module.

[0026] In the air bag apparatus, the gas generator is actuated upon the impact sensor detecting the impact and a working gas is discharged from the gas discharging port of the housing. The working gas flows into the air bag and thereby, the air bag ruptures the module cover and inflates to form a cushion between a passenger and a hard structure in a vehicle to absorb the impact.

[0027] In the gas generator for the air bag of the present invention, by adjusting a shape of the first combustion chamber provided radially in the outside of the inner cylindrical member or adjusting an ejecting position of flames from the ignition means to ignite the first gas generating agent, the ignition of the first gas generating agent in the initial stage of actuation of the gas generator is enhanced. That is, flames of the ignition means ejecting into the first combustion chamber is made to spread widely inside the combustion chamber to ignite more amount of gas generating agents than otherwise.

[0028] Therefore, according to the gas generator for the air bag of the invention, by improving an internal structure thereof, the ignition and combustion performance of the gas generating agent is enhanced, and further, the operation performance of the gas generator is enhanced.

[0029] Next, the present invention provides a gas generator for an air bag capable of downsizing the gas generator and capable of easily and reliably adjusting a capacity of the combustion chamber accommodating the gas generating agent, and provides a retainer for the gas generator as well as an air bag apparatus using the gas generator.

[0030] A retainer of a gas generator for an air bag according to the present invention is used in a gas generator for an air bag in which, in a cylindrical housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall provided with a through-hole is disposed and at least either of an ignition means and gas generator is disposed in the inner cylindrical member, wherein the retainer comprises a cylindrical portion, which is positioned with a distance from an outer peripheral surface of the cylindrical peripheral wall and faces the outer peripheral surface, and a flange-shaped partition wall integrally formed with the cylindrical portion, at least either of the cylindrical portion and the partition wall changes gas-flow ejected from the through-hole formed in the cylindrical peripheral wall and collects combustion products other than gaseous material included in the gas. The combustion products included in the gas are any combustion products, other than gaseous material, such as fluid, semifluid and solid included in the gas ejected from the through-hole.

[0031] A flowing direction of the gas ejected from the through-hole provided in the cylindrical peripheral wall is changed by the cylindrical portion of the retainer. At that time, combustion products, other than gaseous material, such as fluid, semifluid and solid included in the gas collide against the cylindrical portion and/or partition wall. Thereby, the combustion products adhere to the cylindrical portion and/or partition wall or drop to be removed from the gas. The combustion products are collected by the cylindrical portion and/or partition wall of the retainer and thus, it is unnecessary to dispose the coolant means or filter means for removing or reducing the combustion products in the gas ejected from the through-hole and as a result, the producing cost and capacity of the gas generator can be reduced.

[0032] As described above, the retainer of the present invention collects the combustion products in the gas ejected from the through-hole with the cylindrical portion and/or partition wall thereof. When combustion products in the gas ejected from the through-hole is collected by the cylindrical portion, the cylindrical portion is formed in such a size and shape that the combustion product can be collected, and intersection angle with the gas ejected from the through-hole is adjusted. And in this retainer, in order to collect the combustion products more satisfyingly, it is preferable that the cylindrical portion is formed into a size and shape capable of covering at least a communication hole of the inner cylindrical member.

[0033] The retainer of the gas generator for the air bag according to the present invention comprises the cylindrical portion and the flange-shaped partition wall integrally formed with the cylindrical portion, and preferably, the partition wall is formed into a shape and size capable of defining at least the axial end of the first combustion chamber. Therefore, in this case, the partition wall of the retainer has to be formed into a shape and size capable of closing at least an axial end of the first combustion chamber. It is possible to arbitrarily select whether the retainer is formed into a shape and size capable of dividing the coolant means disposed radially in the outside of the combustion chamber and whether the retainer is formed into a shape and size capable of dividing the entire outer space of the inner cylindrical member in the housing into upper and lower portions, depending upon balance of the entire structure in the gas generator. The coolant means is made of laminating wire mesh or expanded metal or the like, and has function to purify or cool a working gas generated by combustion of the gas generating agent.

[0034] Preferably, part of the cylindrical portion is formed into a shape and size capable of fitting outwardly the inner cylindrical member. If the cylindrical portion is used in a gas generator in which the annular coolant means is accommodated in the housing, the cylindrical portion is formed into such a shape and size that part of the cylindrical portion is fitted to an inner peripheral surface or outer peripheral surface of the coolant means or an inner peripheral surface of the housing peripheral wall.

[0035] This retainer can include at least the cylindrical portion, and also include the partition wall. The cylindrical portion is formed into a substantially cylindrical shape, and the partition wall is formed annually and arranged at an axial end of the cylindrical portion in a outwardly or inwardly directed flange-like shape. Further in this retainer, an engaging portion which engages the inner cylindrical member in the housing can be formed into an inwardly directed flange-like shape on the other end of the cylindrical portion. And, if the retainer is fitted outwardly to the inner cylindrical member having the communication hole, preferably, the cylindrical portion faces the communication hole of the inner cylindrical member, and the cylindrical portion has a size to cover the communication hole. In other words, the cylindrical portion is positioned with a distance from the inner cylindrical member at least in the vicinity of the through-hole, and faces the through-hole without closing the same.

[0036] The present invention also provides a gas generator for an air bag by using the above retainer. Namely, the present invention provides a gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall provided with a through-hole, at least either of an ignition means and a gas generating agent disposed inside the inner cylindrical member, and in the outside of the inner cylindrical member, a retainer having a cylindrical portion surrounding a portion of the inner cylindrical member and a flange-shaped partition wall integrally formed on the cylindrical portion, wherein a cylindrical portion of the retainer faces an outer peripheral surface of the cylindrical peripheral wall with a distance, at least either of the cylindrical portion and the partition wall changes a flow of a gas ejected from a through-hole formed in the cylindrical peripheral wall of the inner cylindrical member, and collects combustion products included in the gas.

[0037] And in the gas generator for the air bag in which the first combustion chamber for accommodating the gas generating agent is provided radially in the outside of the inner cylindrical member, preferably, the partition wall of the retainer is formed into a shape and size capable of defining at least the axial end of the first combustion chamber, and the cylindrical portion is formed into a shape and size capable of fitting outwardly the inner cylindrical member.

[0038] In this gas generator, when a step-notched portion is formed by stepwisely notching the outer peripheral surface of the inner cylindrical member in the closure shell side, and an inwardly directed flange-shaped engaging portion is formed on the end of the cylindrical portion of the retainer, the engaging portion is engaged to the notch so that the inner cylindrical member and the retainer can be combined. In this case, the retainer receives pressure of a working gas generated in the first combustion chamber at activation of the gas generator, and thereby the retainer is unfailingly supported and fixed by the inner cylindrical member. Thus, it is possible to easily and reliably control the axial length of the first combustion chamber by this retainer.

[0039] The present invention can be realized by the gas generator in which the inner cylindrical member is disposed in the housing, the ignition means is disposed inside the inner cylindrical member, the first combustion chamber is provided radially in the outside thereof, and flames of the ignition means disposed inside the inner cylindrical member passes through the through-hole provided in the cylindrical peripheral wall of the inner cylindrical member to be ejected into the first combustion chamber. Therefore, the present invention can be realized regardless of other structures, for example, whether two combustion chambers are provided in the housing, a layout thereof and the number of ignition means. In other words, the present invention can be realized even by the gas generator in which the combustion chamber accommodating the gas generating agent is provided radially in the outside of the inner cylindrical member but any combustion chamber is not provided inside the inner cylindrical member. In this case, the ignition means can be accommodated inside the inner cylindrical member.

[0040] In a general aspect of the gas generator according to the present invention, the ignition means is disposed inside the inner cylindrical member, and the first combustion chamber in which the gas generating agent is charged is provided radially in the outside of the inner cylindrical member. The through-hole (hereinafter, this through-hole is referred to as “flame-transferring port”) for ejecting flames generated by actuation of the ignition means into the first combustion chamber is formed in the cylindrical peripheral wall of the inner cylindrical member. The gas generating agent (“first gas generating agent” hereinafter) in the first combustion chamber is ignited and burnt by flames ejected from the flame-transferring port.

[0041] According to the gas generator of the present invention using the retainer having the partition wall, the axial length of the combustion chamber can be controlled by the retainer, so that, by appropriately adjusting the shape and location of the retainer, it is possible to shorten the axial length of the first combustion chamber. As a result, flames ejected from the flame-transferring port can be spread over the entire first combustion chamber, and the first gas generating agent accommodated in the first combustion chamber can effectively be ignited. When the retainer is disposed on the axial end of the first combustion chamber, the flow-path through which a working gas passes can be formed on the other side of the retainer to the first combustion chamber.

[0042] If the retainer is disposed as described above and the axial length of the first combustion chamber is adjusted to enhance the ignition performance of the first gas generating agent, even with the first gas generating agent used in the gas generator not having a satisfying ignition performance, the ignition performance of the gas generating agent can be compensated. In other words, by controlling the shape of the first combustion chamber or an arrangement of a flame-transferring port, even the gas generating agent without a satisfying ignition performance can be used as the first gas generating agent. Improvement on the ignition performance of the gas generating agent can be measured, for example, by the time when the maximum pressure inside the gas generator at activation can be obtained, or a tank curve (pressure time curve in 60-liter tank) obtained by the 60-liter tank test (tank combustion test).

[0043] The gas generator can constitute an air bag apparatus together with an impact sensor to detect the impact and actuate the gas generator, an air bag to introduce a gas generated in the gas generator and inflate and a module case for accommodating the air bag.

[0044] The gas generator is accommodated in the module case together with the air bag (bag body) for introducing a generated gas to inflate and is provided as a pad module.

[0045] In the air bag apparatus, the gas generator is actuated upon the impact sensor detecting the impact and a working gas is discharged from the gas discharging port of the housing. The working gas flows into the air bag and thereby, the air bag ruptures the module cover and inflates to form a cushion between a passenger and a hard structure in a vehicle to absorb the impact.

[0046] In the gas generator of the present invention, if the second gas generating agent generates solid combustion products such as fluid or semifluid, by arranging the retainer of the present invention to face the communication hole of the inner cylindrical member, the solid combustion products can be collected by the retainer. And by collecting the solid combustion products by the retainer in this manner, the an heat amount of a working gas generated by combustion of the second gas generating agent is reduced and as a result, it is possible to reduce an amount of coolant means and cooling ability thereof used for cooling the working gas.

[0047] When the retainer is fixed by being hooked on a step portion of an inner cylindrical member and by being interposed between the first and second coolant means, working gases generated in the respective combustion chambers are not leaked to each other chambers. In this case, since the retainer can be disposed without being press-inserted, the assembling can be facilitated. Further, the retainer is pushed towards the step-notched portion of the inner cylindrical member by the combustion pressure of the first gas generating agent, so that they can be more tightly attached to each other.

[0048] When the coolant means is divided by the retainer of the present invention and working gases generated in the respective combustion chambers pass through different coolant means, the coolant means is independent from each other, and thereby the operation output of the gas generator can be adjusted easily.

[0049] Further, the present invention provides a gas generator for an air bag in which two combustion chambers are provided in the housing and combustion degrees of the gas generating agents in the respective combustion chambers can independently be adjusted, and that can be produced easily and smaller.

[0050] The present invention provides gas generator for an air bag comprising, in a housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall, two combustion chambers divided by the inner cylindrical member, gas generating agents stored in the respective chambers to be burnt for generating a working gas, wherein working gases generated in the respective combustion chambers pass through different flow-paths and then, reach the gas discharging port.

[0051] The inner cylindrical member includes a cylindrical peripheral wall, and the wall defines the combustion chamber. Generally, the ignition means provided to ignite the gas generating agent is preferably accommodated inside the inner cylindrical member. Only single inner cylindrical member is disposed in the housing, and preferably, the combustion chambers are defined inside and outside the inner cylindrical member. It is preferable that all ignition means included in the gas generator is accommodated inside the inner cylindrical member. In this case, the inner cylindrical member defining the combustion chambers and the inner cylindrical member accommodating the ignition means are the same (that is, a single cylindrical member).

[0052] The flow-path of a working gas is a course (or flowing manner) of a working gas inside the housing. That the flow-paths of working gases generated in the respective combustion chambers are different from each other indicates that the course of the working gas generated in one combustion chamber is different at least in any part from a course of a working gas generated in another combustion chamber. Therefore, if a working gas generated in one combustion chamber directly passes through the coolant means provided radially in the outside of the chamber, the respective flow-paths of the working gases are different from each other as long as a working gas generated in another combustion chamber does not follow the course from said one combustion chamber to the coolant means.

[0053] As described above, by making separate flow-paths of working gases for the respective combustion chambers, it is possible to easily adjust the generation of working gases in the respective combustion chambers.

[0054] By dividing the two combustion chamber with the inner cylindrical member having the cylindrical peripheral wall and accommodating the ignition means inside the inner cylindrical member, the gas generator can be reduced in size.

[0055] That is, according to the present invention, the gas generator for the air bag can be reduced in size, and combustion degree of the gas generating agent in the combustion chamber can be independently adjusted at each chamber.

[0056] The present invention also provides a gas generator for an air bag in which a working gas generated in one of the two combustion chambers provided in the housing reaches a gas discharging port without flowing into the other combustion chamber. With this structure, the working gas generated in one of the combustion chambers does not concern the combustion of a gas generating agent in the other combustion chamber, and the combustion of the gas generating agent in each combustion chamber can be independently adjusted.

[0057] If the housing is defined such that a working gas generated in one of the combustion chambers passes through the flow-space defined by the other combustion chamber, a working gas generated in one of the combustion chambers does not flow into the other combustion chamber. This flow-space can be, for example, divided by the retainer defining the end of the other combustion chamber.

[0058] In the gas generator mentioned above, working gases generated in the respective combustion chambers can be made to reach the gas discharging port through different coolant means. Also, the working gases can be made to reach different gas discharging ports.

[0059] When different gas discharging ports or coolant means are formed for working gases generated in the respective combustion chambers, naturally, these gas discharging ports or coolant means have to be provided to correspond to the respective combustion chambers. In other words, exclusively for a working gas generated in one combustion chamber, a gas discharging port and/or a closure shell are provided.

[0060] When different gas discharging ports or coolant means are formed for working gases generated in the respective combustion chambers, a flow-space of a working gas is formed in the housing so that a working gas generated in one of the combustion chambers passes through the flow-space. Also in this case, two flow-spaces may be formed in the housing so that working gases generated in the respective combustion chambers pass through different flow-spaces.

[0061] For example, the flow-space communicating one of the combustion chambers can be obtained such that, after a retainer is provided in the other combustion chamber to define an end portion of the other combustion chamber, a space is defined on the other side of the retainer to said other combustion chamber. In this case, at least a partition wall for defining an end of said other combustion chamber has to be provided with the retainer, and additionally, a structure to be supported and fixed inside the housing also has to be provided with the retainer. An example of such a retainer can be obtained by forming a cylindrical portion in a substantially cylindrical shape and an outwardly or inwardly directed flange-shaped partition wall integrally. The retainer obtained in this manner can be supported and fixed inside the housing by fitting the cylindrical portion outwardly or inwardly a member arranged on an inner wall portion of the housing or inside the housing.

[0062] In addition to defining with a retainer, the flow-space can be obtained by a member (e.g., the inner cylindrical member) having a cylindrical peripheral wall for defining the combustion chambers or by changing a structure of the housing.

[0063] In the gas generator formed in the above-described manner, working gases generated in the two combustion chambers reach the coolant means or gas discharging port through different flow-paths. That is, the one combustion chamber and the other combustion chamber communicate each other spatially through the coolant means, but a working gas generated in one of the combustion chambers never affect the combustion of the gas generating agent accommodated in the other combustion chamber. Therefore, even if both the combustion chambers communicate each other through a little gap, the generation of the working gases in each combustion chamber can be independently adjusted as long as a working gas generated in one of the combustion chambers does not affect the combustion of gas generating agent accommodated in the other combustion chamber.

[0064] Accordingly, in the gas generator of the present invention, when the gas generating agent in one of the combustion chambers is burnt, the gas generating agent in the other combustion chamber burns without receiving any influence of combustion pressure or combustion heat generated in said one combustion chamber. As a result, it is possible to adjust the combustion of the gas generating agent accommodated in each combustion chamber independently, i.e., it is possible to easily and reliably adjust the operation performance of the gas generator.

[0065] Further, by forming different paths from the respective combustion chambers to the coolant means, flames can be hardly transferred between the combustion chambers. As a result, when a seal tape seals off the combustion chamber from the flow-space, a seal tape in which a rupturing strength is not so high or melting point is low, e.g., aluminum seal tape having metal layer of 80 μm can be used.

[0066] The gas generator for the air bag of the invention can be realized by the following gas generator, for example. That is, in a cylindrical housing comprising a diffuser shell which is formed in a cylindrical shape with a top and has a gas discharging port, and a closure shell forming the inner space together with a diffuser shell, an inner cylindrical member defining an inner space inside the housing is disposed and a first combustion chamber is provided radially in the outside thereof. The inside of the inner cylindrical member is divided by a partition wall such that the divided portions are adjacent to each other axially, and one of the divided portions in the diffuser shell side is defined as the second combustion chamber and the other in the closure shell side is defined as the ignition means accommodating chamber. A gas generating agent is charged into each combustion chamber, and an ignition means to initiate activation of the gas generator is arranged in the ignition means accommodating chamber. Annular coolant means made of laminated wire mesh to cool or purify a working gas generated in each combustion chamber is disposed radially in the outside of the first combustion chamber.

[0067] And in this gas generator, for example, after the retainer is disposed on an axial end of the first combustion chamber to close the axial end of the first combustion chamber, the flow-space of a working gas can be formed between the retainer and an inner surface of the diffuse shell. In this case, the peripheral wall of the inner cylindrical member is provided with a communication hole, and the second combustion chamber and the flow-space communicate each other through the communication hole.

[0068] Since two combustion chambers are provided in the gas generator of the present invention, it is preferable that the gas generating agents in the respective combustion chambers can be burnt at different timing. Therefore, in the gas generator for the air bag of the invention, the ignition means in which the activation timings can be arbitrarily differed, for example, using two igniters is optimally used.

[0069] The gas generator can constitute an air bag apparatus together with an impact sensor to detect the impact and actuate the gas generator, an air bag to introduce a gas generated in the gas generator and inflate and a module case for accommodating the air bag.

[0070] The gas generator is accommodated in the module case together with the air bag (bag body) for introducing a generated gas to inflate and is provided as a pad module.

[0071] In the air bag apparatus, the gas generator is actuated upon the impact sensor detecting the impact and a working gas is discharged from the gas discharging port of the housing. The working gas flows into the air bag and thereby, the air bag ruptures the module cover and inflates to form a cushion between a passenger and a hard structure in a vehicle to absorb the impact.

[0072] In the gas generator for an air bag according to the present invention, though the overall size of the gas generator is limited, working gases generated in the respective combustion chambers can flow towards the coolant means via different flow-paths so that the combustion of the gas generating agent in each combustion chamber is independently adjusted, and thereby the operation output of the gas generator can be easily adjusted. As a result, it is possible to reduce a weight of the coolant means. This becomes remarkable when different coolant means or different gas discharging ports are formed for the respective combustion chambers.

[0073] Especially in the gas generator obtaining the flow-space by the retainer as described in the embodiment, it is possible to enhance the ignition of the first gas generating agent in the initial stage of actuation of the gas generator by adjusting a shape of the first combustion chamber provided radially in the outside of the inner cylindrical member or by adjusting an ejecting location of flames from the ignition means which ignites the first gas generating agent. In other words, by allowing flames of the ignition means ejected into the first combustion chamber to spread widely in the combustion chamber, more amount of gas generating agents can be ignited than otherwise.

[0074] Some of the above gas generators and retainers can be structured by incorporating each other's elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0075]FIG. 1 is a vertical sectional view showing a gas. generator for an air bag of one embodiment.

[0076]FIG. 2 are partial vertical sectional views showing the gas generator for the air bag of other embodiment.

[0077]FIG. 3 is a partial vertical sectional view showing the gas generator for the air bag of other embodiment.

[0078]FIG. 4 are partial vertical sectional views showing the gas generator for the air bag of other embodiment.

[0079]FIG. 5 is a vertical sectional view showing the gas generator for the air bag of other embodiment.

[0080]FIG. 6 is a vertical sectional view showing the gas generator for the air bag of other embodiment.

[0081]FIG. 7 are vertical sectional views of an essential portion showing other aspects of a retainer.

[0082]FIG. 8 are vertical sectional views showing the gas generator for the air bag of other embodiment.

[0083]FIG. 9 are vertical sectional views showing the gas generator for the air bag of other embodiment.

[0084]FIG. 10 is vertical sectional views showing the gas generator for the air bag of other embodiment.

[0085]FIG. 11 is vertical sectional views showing the gas generator for the air bag of other embodiment.

[0086] The numerals in the drawings will be explained.

[0087]3 housing

[0088]4 inner cylindrical member

[0089]5 a and 5 b combustion chamber

[0090]7 partition wall

[0091]9 a and 9 b gas generating agent

[0092]12 ignition means accommodating chamber

[0093]16 transfer charge

[0094]17 a, 17 flame-transferring port

[0095]22 a and 22 b coolant means

[0096]22 a and 23 b igniter

[0097]25 gap

[0098]26 gas discharging port

[0099]50 retainer

[0100]51 inner wall portion or cylindrical portion

[0101]52 partition wall surface

[0102]54 underplate

[0103]55 flow-path or flow-space

PREFERRED EMBODIMENTS OF THE INVENTION

[0104] A gas generator for an air bag of the present invention will be explained based on the drawings showing preferred embodiments.

[0105]FIG. 1 is a vertical sectional view showing one embodiment of the gas generator for the air bag of the present invention.

[0106] The gas generator shown in this embodiment has two combustion chambers in a housing and two ignition means respectively corresponding to the combustion chambers. More specifically, in the housing 3 formed by joining a diffuser shell 1 having the gas discharging port 26 and a closure shell 2 forming an inner accommodating space together with the diffuser shell 1, an inner cylindrical member 4 in a substantially cylindrical shape is disposed and the outside thereof is a first combustion chamber 5 a. An interior of the inner cylindrical member 4 is divided into two chambers by a partition wall 7, one chamber closer to the diffuser shell is a second combustion chamber 5 b and the other chamber closer to the closure shell is an ignition means accommodating chamber 12.

[0107] Gas generating agents 9 a and 9 b are charged into the respective two combustion chambers 5 a and 5 b defined in the housing 3. The first gas generating agent 9 a is charged into the first combustion chamber 5 a, and the second gas generating agent 9 b is charged into the second combustion chamber 5 b. Each of the gas generating agents is ignited and burnt by actuation of the ignition means to generate a working gas for inflating an air bag. Shapes, compositions, composition ratios and amounts of the first and second gas generating agents 9 a and 9 b in the respective chambers may be different from each other. Especially in this embodiment, the first gas generating agent 9 a is a gas generating agent including fuel and oxidizing agent. Guanidine derivatives or a mixture thereof is used as the fuel. Basic copper nitrate is used as the oxidizing agent.

[0108] A retainer 50 having an annular partition wall portion 52 is disposed on an axial end of the first combustion chamber 5 a in the diffuser shell 1 side. The partition wall portion 52 defines an axial length of the first combustion chamber 5 a. In the gas generator shown in FIG. 1, the retainer 50 is formed into an outwardly directed flange-shape, and its inner wall portion 51 is engaged to a step-notched portion 53 of an outer peripheral surface of the inner cylindrical member 4.

[0109] In the retainer 50, by adjusting the location thereof or the position of the partition wall portion 52, an inner shape, a capacity and the like of the first combustion chamber 5 a can be adjusted. Therefore, it is possible to adjust a ratio (D/L) of a radial average distance (D) of the combustion chamber 5 a to an axial average length (L) of the combustion chamber 5 a to be in the range of 0.2 to 2.0, preferably of 0.4 to 1.0 by adjusting the shape or position of the retainer 50. In this embodiment, and an end surface of the first combustion chamber 5 a in the closure shell 2 side is defined by an inner surface of the closure shell 2, and the gas generating agent 9 a in the combustion chamber 5 a is supported by an underplate 54.

[0110] The retainer 50 shown in this embodiment defines a flow-path 55 on the opposite side the first combustion chamber 5 a so that a working gas generated by combustion of the second gas generating agent 9 b passes through the flow-path. The flow-path 55 and the second combustion chamber 5 b can communicate with each other through a communication hole 10 formed in a partition wall of the inner cylindrical member 4.

[0111] An ignition means including two igniters 23 a and 23 b and a transfer charge 16 charged into an aluminum cup is accommodated in the ignition means accommodating chamber 12. The two igniters 23 a and 23 b are fixed to a collar assembly 31. The collar assembly 31 is fixed by crimping a lower end 4 a of the inner cylindrical member 4. The first igniter 23 a and the second igniter 23 b are accommodated in spaces defined by the partition wall 7 respectively. The transfer charge 16 is arranged above the first igniter 23 a in the space where the first igniter 23 a is accommodated.

[0112] The space in which the first igniter 23 a is accommodated and the first combustion chamber 5 a can communicate with each other through a first flame-transferring port 17 a formed in a peripheral wall of the inner cylindrical member 4. The first flame-transferring port 17 a is formed such that a distance L₁ from the center of the axial average length measured from the inner bottom surface of the closure shell in the first combustion chamber to the center of the first flame-transferring hole 17 a is not more than ¼ of the axial average length L in the first combustion chamber, and preferably, the flame-transferring port 17 is formed at the center of the first combustion chamber 5 a in the axial direction. With this design, flames caused by combustion of the transfer charge 16 is ejected to the substantially central position of the first combustion chamber 5 a, and the flames of the transfer charge 16 can reach the entire first combustion chamber 5 a.

[0113] Meanwhile, the space where the second igniter 23 b is accommodated and the second combustion chamber 5 b can communicate with each other through a second flame-transferring port 17 b formed in the partition wall 7. And the second combustion chamber 5 b can communicate with a flow-path 55 defined by the retainer 50 through the communication hole 10 formed in the inner cylindrical member 4.

[0114] Working gases generated by combustion of the first gas generating agent 9 a and the second gas generating agent 9 b passes through annular coolant means 22 comprising laminated wire mesh or expanded metal to be discharged from a gas discharging port 26. Especially in this embodiment, the working gases generated from gas generating agents 9 a and 9 b pass through different coolant means 22 a and 22 b. More specifically, the first coolant means 22 a is disposed radially in the outside of the first combustion chamber 5 a, the second coolant means 22 b is disposed radially in the outside the second combustion chamber 5 b through the flow-path 55, and both the coolant means 22 a and 22 b are separated from each other by the retainer 50.

[0115] Therefore, in the gas generator shown in this embodiment, the transfer charge 16 is burnt by actuation of the first igniter 23 a, and its flame passes through the first flame-transferring port 17 a and is ejected into the first combustion chamber 5 a. Consequently, the first gas generating agent 9 a is ignited and burnt to generate a working gas, the working gas passes through the first coolant means 22 a and reaches a gap 25 to be discharged from the gas discharging port 26. On the other hand, when the second igniter 23 b is actuated, its flame passes through the second flame-transferring port 17 b and is ejected into the second combustion chamber 5 b to ignite and burn the second gas generating agent 9 b. The working gas generated by combustion of the second gas generating agent 9 b flows into the flow-path 55 from the communication hole 10, passes through the flowpath path 55 and reaches the second coolant means 22 b. The working gas is cooled and purified while passing through the second coolant means 22 b, and then passes through the gap 25 to be discharged from the gas discharging port 26.

[0116] Especially in the embodiment shown in FIG. 1, the retainer 50 is formed into an outwardly directed flange-like shape, and the end of the inner wall portion 51 is engaged to the step-notched portion 53 formed in the outer peripheral surface of the inner cylindrical member 4. Since the communication hole 10 is formed to face the inner wall 51, a working gas which is generated by combustion of the second gas generating agent 9 b to be discharged from the communication hole 10 once collides against the inner wall portion 51 of the retainer. Therefore, for example, if the second gas generating agent 9 b generates solid combustion products such as fluid or semifluid at the time of combustion, the combustion products collides against the inner wall portion 51 and are removed from the working gas.

[0117] Further, in the gas generator shown in this drawing, the two coolant means 22 a and 22 b are separately disposed, so that the purifying/cooling abilities of the coolant means 22 a and 22 b can be controlled respectively in accordance with the generation amount of a working gas generated in the combustion chambers 5 a and 5 b. And, if the second coolant means 22 b cools a working gas generated by combustion of the second gas generating agent 9 b, an inner diameter of the first coolant means 22 a can be made larger, and thereby, the radial average distance (D) of the first combustion chamber 5 a can be increased.

[0118] In FIG. 1, a numeral 11 represents a seal tape for closing the communication hole 10, a numeral 18 represents a seal tape for closing the first flame-transferring port 17 a, and a numeral 27 represents a seal tape for closing the gas discharging port 26. The seal tapes are ruptured when flames or gases pass through the holes or ports.

[0119] The retainer 50 shown in this embodiment ensure the axial end of the first combustion chamber 5 a, defines the flow-path 55 and separates the coolant means 22 a and 22 b from each other.

[0120]FIG. 2 are sectional views of essential portions of gas generators in which the axial average length (L) of the first combustion chamber is defined by using retainers having different shapes from that shown in FIG. 1. In all of aspects (a to g) shown in FIG. 2, the axial average length (L) of the first combustion chamber 5 a is defined by the retainer 50 disposed on the axial end of the first combustion chamber. In the aspects shown in FIGS. 2(a) to (g), the flow-path is provided on the opposite side to the first combustion chamber. In an aspect shown in FIG. 2(h), the axial length of the first combustion chamber is defined, and a retainer 50 forming no flow-path is provided on the opposite side to the first combustion chamber. In FIGS. 2 (a) to (h), each of members and portions is designated with the same numeral as that in FIG. 1, and a description thereof is omitted.

[0121]FIG. 3 is a sectional view of an essential portion showing a gas generator for an air bag in which the axial length of the first combustion chamber is limited with an inner surface of the housing by bending the inner cylindrical member 4 into a flange-like shape. In the gas generator shown in this aspect, a working gas ejected from the through-hole 10 is directly ejected to the coolant means 22. In FIG. 3, each of members and portions is designated with the same numeral as that in FIG. 1, and a description thereof is omitted.

[0122] Further, FIG. 4 are sectional views of essential portions of gas generators in which the axial average length (L) of the first combustion chamber is limited by an inner surface of the housing. FIGS. 4(a) to (f) shows various aspects for limiting the axial average length (L) of the first combustion chamber by an inner surface of the housing. In FIGS. 4(a) to (f), each of members and portions is designated with the same numeral as that of FIG. 1, and a description thereof is omitted.

[0123] The gas generator for an air bag of the present invention may employ embodiments shown in FIGS. 5 and 6. In FIGS. 5 and 6, each of members and portions is designated with the same numeral as that of FIG. 1, and a description thereof is omitted.

[0124] In a retainer 50 shown in FIG. 5, the axial end of the first combustion chamber 5 a is defined, and the axial average length of the first combustion chamber 5 a is adjusted. However, the retainer 50 does not divide the coolant means 22. Therefore, a working gas generated in the second combustion chamber 5 b flows into the flow-path 55 through the communication hole 10, the gas passes through the same coolant means 22 as the working gas generated in the first combustion chamber 5 a passes through, and then passes through the gap 25 to be discharged from the gas discharging port 26. In this case, even if the working gas is generated only in the first combustion chamber 5 a and the gas generating agent in the second combustion chamber 5 b is not yet ignited, the working gas generated in the first combustion chamber 5 a opens the gas discharging port 26 and therefore, the gas does not flow into the flow-path 55 through the coolant means 22 to rupture the seal tape 11 which closes the communication hole 10.

[0125] In FIG. 6, a retainer 50 defines the axial end of the first combustion chamber 5 a and adjusts the axial average length (L) of the first combustion chamber 5 a. And an outer wall end surface of the retainer 50 abuts against an inner wall surface of the diffuser shell 1 to separate flow-paths for a working gas generated in the first combustion chamber 5 a and a working gas generated in the second combustion chamber 5 b from each other. Therefore, a working gas generated in the first combustion chamber 5 a is discharged from the gas discharging port 26 a, and a working gas generated in the second combustion chamber 5 b is discharged from the gas discharging port 26 b.

[0126] The air bag apparatus of the present invention using the above-described gas generator for the air bag comprises an actuation signal-outputting means including an impact sensor and a control unit, and a module case including the air bag gas generator 100 and an air bag. The air bag gas generator 100 is connected to the actuation signal-outputting means (the impact sensor and the control unit) on the first and second igniters 23 a and 23 b side. In the air bag apparatus having such a structure, by appropriately setting an actuation signal outputting condition in the actuation signal outputting means, it is possible to adjust the gas generation amount in accordance with a degree of an impact and to adjust an expansion speed of the air bag. As a structure of other than the gas generator in this air bag apparatus, one disclosed in JP-A No. 11-334517 can be employed.

[0127] The gas generator for the air bag of the present invention will be explained based on the drawings showing a preferred embodiment.

[0128]FIG. 1 is a vertical sectional view showing one embodiment of the gas generator for the air bag of the invention.

[0129] The gas generator shown in this embodiment has two combustion chambers in the housing and two ignition means respectively corresponding to the combustion chambers. More specifically, the housing 3 formed by joining a diffuser shell 1 having a gas discharging port 26 and a closure shell 2 forming an inner accommodating space together with the diffuser shell 1. An inner cylindrical member 4 in a substantially cylindrical shape is disposed in the housing 3, and the outside thereof is the first combustion chamber 5 a. An interior of the inner cylindrical member 4 is divided into the two chambers by a partition wall 7, one of the chambers closer to the diffuser shell is a second combustion chamber 5 b, and the other chamber closer to the closure shell is an ignition means accommodating chamber 12. The partition wall 7 is engaged to a step-notched portion 6 formed in an inner surface of the inner cylindrical member 4. In this embodiment also, a cylindrically formed peripheral wall (i.e., cylindrical peripheral wall) of the inner cylindrical member 4 is formed with a through-hole. In this embodiment, among the through-holes, the one which is open at the second combustion chamber is the communication hole 10, and the other one which is open at the ignition means accommodating chamber 12 is the first flame-transferring port 17 a.

[0130] Gas generating agents 9 a and 9 b are charged into the respective two combustion chambers 5 a and 5 b defined in the housing 3. The first gas generating agent 9 a is charged into the first combustion chamber 5 a, and the second gas generating agent 9 b is charged into the second combustion chamber 5 b. Each of the gas generating agents is ignited and burnt by actuation of the ignition means to generate a working gas for inflating an air bag. Shapes, compositions, composition ratios and amounts of the first and second gas generating agent 9 a and 9 b in the respective combustion chambers may be different from each other. Especially in this embodiment, the first gas generating agent 9 a is a gas generating agent including fuel and oxidizing agent. Guanidine derivatives or a mixture thereof is used as the fuel. Basic copper nitrate is used as the oxidizing agent. The same material as that of the first gas generating agent is used for the second gas generating agent 9 b as well.

[0131] A retainer 50 having a cylindrical portion 51 in a shape such as to surround a cylindrical peripheral wall of the inner cylindrical member and an annular partition wall portion 52 is disposed on the axial end in the diffuser shell 1 side of the first combustion chamber 5 a. The partition wall portion 52 defines the axial length of the first combustion chamber 5 a. That is, the retainer 50 comprises the cylindrical portion 51 disposed to face the inner cylindrical member at a predetermined distance and the annular partition wall portion 52 which is bent outwardly into a flange-like shape from the cylindrical portion 51. And further, an inwardly directed flange-like engaging portion 56 is formed opposite to the partition wall portion 52 on the cylindrical portion 51. An outer periphery of the inner cylindrical member is formed with a step-notched portion 53 formed by stepwisely notching the outer periphery in the closure shell 2 side. The retainer 50 is disposed and fixed by engaging the engaging portion 56 to the step-notched portion 53. In the retainer 50 shown in FIG. 1, when the first gas generating agent is burnt at activation of the gas generator, the retainer 50 is pushed in a supporting direction by the step-notched portion 53 by the combustion pressure, and a fixed state and ignition state thereof become further reliable.

[0132] In the retainer 50 shown in this embodiment, since the cylindrical portion 51 is disposed to face the communication hole 10 without closing the same, a working gas which is generated by combustion of the second gas generating agent 9 b and discharged from the communication hole 10 once collides against the cylindrical portion 51. Therefore, if the second gas generating agent 9 b generates solid combustion products such as fluid or semifluid at the time of combustion, the combustion products collide against the cylindrical portion 51 and are removed from the working gas. As a result, when the gas generating agent generating such solid combustion products is used as the second gas generating agent 9 b, the solid combustion products are largely removed by the cylindrical portion 51, so that an amount of the later-described second coolant means 22 b and a thickness thereof in the radial direction can be reduced.

[0133] In the retainer 50, by adjusting the location thereof or the position of the partition wall portion 52, an inner shape, a capacity and the like of the first combustion chamber 5 a can be adjusted. Therefore, it is possible to adjust a ratio (D/L) of a radial average distance (D) of the combustion chamber 5 a to an axial average length (L) of the combustion chamber 5 a to be in the range of 0.2 to 2.0, preferably of 0.4 to 1.0 by adjusting the shape or position of the retainer 50. In this embodiment, and end surface 2 of the first combustion chamber 5 a in the closure shell 2 side is defined by an inner surface of the closure shell 2, and the gas generating agent 9 a in the combustion chamber 5 a is supported by an underplate 54.

[0134] The retainer 50 shown in this embodiment defines a flow-path 55 on the opposite side to the first combustion chamber 5 a so that a working gas generated by combustion of the second gas generating agent 9 b passes through the flow-path. The flow-path 55 and the second combustion chamber 5 b can communicate with each other through a communication hole 10 formed in a partition wall of the inner cylindrical member 4.

[0135] An ignition means including two igniters 23 a and 23 b and a transfer charge 16 charged into an aluminum cup is accommodated in the ignition means accommodating chamber 12. The two igniters 23 a and 23 b are fixed to a collar assembly 31. The collar assembly 31 is fixed by crimping a lower end 4 a of the inner cylindrical member 4. The first igniter 23 a and the second igniter 23 b are accommodated in spaces, inside the inner cylindrical member, defined by the partition wall 7 respectively. The transfer charge 16 is arranged above the first igniter 23 a in the space where the first igniter 23 a is accommodated. The igniters 23 a and 23 b stored in the ignition accommodating chamber 12 are arranged such that flames generated by activation of the first igniters 23 a does not mix with flames generated by activation of the second ignites 23 b.

[0136] The space in which the first igniter 23 a is accommodated and the first combustion chamber 5 a can communicate with each other through a flame-transferring port 17 a formed in a peripheral wall of the inner cylindrical member 4. In FIG. 1, the flame-transferring port 17 a is formed such that a distance L₁ from the center of the axial average length in the first combustion chamber to the center of the flame-transferring hole 17 a is not more than ¼ of the axial average length L in the first combustion chamber. Preferably, the flame-transferring port 17 is formed at the center of the first combustion chamber 5 a in the axial direction. With this design, flames caused by combustion of the transfer charge 16 is ejected to the substantially central position of the first combustion chamber 5 a, and the flames of the transfer charge 16 can reach the entire first combustion chamber 5 a.

[0137] Meanwhile, the space where the second igniter 23 b is accommodated is formed to communicate the second combustion chamber 5 b, the second combustion chamber 5 b can communicate a flow-path 55 defined by the retainer 50 through a communication hole 10 formed in the inner cylindrical member 4.

[0138] Working gases generated by combustion of the first gas generating agent 9 a and the second gas generating agent 9 b passes through annular coolant means 22 comprising laminated wire mesh or expanded metal to be discharged from a gas discharging port 26. Especially in this embodiment, the working gases generated from gas generating agents 9 a and 9 b pass through different coolant means 22 a and 22 b. More specifically, the first coolant means 22 a is disposed radially in the outside of the first combustion chamber 5 a, the second coolant means 22 b is disposed radially in the outside the second combustion chamber 5 b through the flow-path 55, and both the coolant means 22 a and 22 b are separated from each other by the retainer 50.

[0139] Therefore, in the gas generator shown in this embodiment, the transfer charge 16 is burnt by actuation of the first igniter 23 a, and its flame passes through the first flame-transferring port 17 a and is ejected into the first combustion chamber 5 a. Consequently, the first gas generating agent 9 a is ignited and burnt to generate a working gas, the working gas passes through the first coolant means 22 a, reaches a gap 25 and rupture a seal tape 27 to be discharged from the gas discharging port 26. On the other hand, when the second igniter 23 b is actuated, its flame is ejected into the second combustion chamber 5 b to ignite and burn the second gas generating agent 9 b. The working gas generated by combustion of the second gas generating agent 9 b is ejected outwardly from the communication hole 10 in the radial direction, and its direction is changed by the cylindrical portion 51 of the retainer 50. At the same time, the combustion products included in the working gas collide against the cylindrical portion 51. Consequently, most of the combustion products included in the working gas generated by combustion of the second gas generating agent 9 b are removed or reduced. The working gas whose direction has been changed by the cylindrical portion 51 proceeds to and passes through the flow-path 55 to reach the second coolant means 22 b. The working gas is cooled while it passes through the second coolant means 22 b, and is purified and discharged from the gas discharging port 26 via the gap 25. When different coolant means are used for the respective working gases generated in each the combustion chamber, the respective coolant means are independent from each other, so that the actuation output of the gas generator can be adjusted easily.

[0140] Further, in the gas generator shown in this drawing, the two coolant means 22 a and 22 b are separately disposed, so that the purifying/cooling abilities of the coolant means 22 a and 22 b can be controlled respectively in accordance with the generation amount of a working gas generated in the combustion chambers 5 a and 5 b. And, if the second coolant means 22 b cools a working gas generated by combustion of the second gas generating agent 9 b, an inner diameter of the first coolant means 22 a can be made larger, and thereby, the radial average distance (D) of the first combustion chamber 5 a can be increased.

[0141] In FIG. 1, a numeral 11 represents a seal tape for closing the communication hole 10, a numeral 18 represents a seal tape for closing the first flame-transferring port 17 a, and a numeral 27 represents a seal tape for closing the gas discharging port 26. The seal tapes are ruptured when flames or gases pass through the holes or ports.

[0142] In the above-described embodiment shown in FIG. 1, the retainer 50 shown in this embodiment ensure the axial end of the first combustion chamber 5 a, defines the flow-path 55 and separates the coolant means 22 a and 22 b from each other.

[0143] The retainer 50 may employ any of aspects shown in FIGS. 7(a) to (f). If the axial average length (L) of the first combustion chamber is defined, the aspect shown in FIGS. 7(g) and (h) can be employed. That is, in the aspects shown in FIGS. 7(a) to (f) , the axial average length (L) of the first combustion chamber is defined by the retainer 50, a distance L₁ from the center of an axial average length to the center of the flame-transferring port 17 a in the first combustion chamber 5 a is adjusted to be not more than ¼ of the axial average length (L) of the first combustion chamber 5 a.

[0144] In the retainer 50 shown in each of FIGS. 7(a) and (f), part of the cylindrical portion 51 is fitted outwardly to the inner cylindrical member 4 or fitted to an inner peripheral surface or outer peripheral surface of the coolant means 22 a, or fitted into the inner peripheral surface of the housing 3 so that part of the cylindrical portion 51 is supported and fixed in the housing.

[0145] Particularly, the retainer 50 shown in each of FIGS. 7(a) and (f) includes the inner cylindrical portion 51 and the partition wall portion. In the aspects shown in FIGS. 7(a), (c), (d) and (f), a gas ejected from the communication hole 10 collides against the cylindrical portion 51, the combustion products in the gas are collected by the cylindrical portion 51. In the aspect shown in FIG. 7(e), a gas ejected from the communication hole 10 collides against the partition wall portion 52, and the combustion products in the gas are collected by the partition wall portion 52. In the aspect shown in FIG. 7(e), however, the gas which previously passed through the second coolant means 22 b is ejected from the communication hole 10. Therefore, if the combustion products are further collected by the cylindrical portion 51, a gas further purified is discharged from the gas discharging port 26. In the aspect shown in FIG. 7(b), a gas ejected from the communication hole 10 is previously purified by second the coolant means 22 b and in this state, the gas collides against the cylindrical portion 51. Consequently, the combustion products can be removed more unfailingly.

[0146] In the aspects shown in FIGS. 7(a) and (b), the cylindrical portion 51 of the retainer is divided into a portion which is fitted outwardly to the inner cylindrical member 4 and a portion facing the communication hole 10, and the partition wall portion 52 is provided between both the portions. That is, in the retainer 50 of the present invention, the cylindrical portion 51 does not necessarily have to be arranged in a single position but can be arranged in different positions such as a portion for supporting and fixing the retainer 50 in the housing and a position for covering the communication hole 10. In the aspects shown in FIGS. 7(a) and (b), the direction of a gas ejected from the through-hole 10 is changed by a portion of the retainer 50 which faces the communication hole 10, and the combustion products are collected.

[0147] In the retainer 50 shown in FIG. 7(h), the partition wall portion 52 is inclined in an outwardly directed flange-like shape from the cylindrical portion 51 which is fitted outwardly to the inner cylindrical member 4, and a tip end of the cylindrical portion 51 and a tip end of the partition wall portion 52 are connected to each other. With this arrangement, a cross section of the retainer 50 in the axial direction is of substantially right triangle, and its hypotenuse is the partition wall portion 52. In the retainer 50 shown in FIG. 7(h), the axial length of the first combustion chamber 5 a is defined but the flow-path is not formed on the opposite side to the first combustion chamber.

[0148] In the aspects shown in FIGS. 7(a) to (g), the retainer 50 is provided with the flow-path 55 on the opposite side to the first combustion chamber 5 a.

[0149] In FIGS. 7(a) to (h), each of members and portions which is the same as that in the gas generator shown in FIG. 1 is designated with the same numerals, and a description thereof is omitted. A numeral 22 in FIG. 7 represents a filter means.

[0150] The gas generator for an air bag of the present invention may employ embodiments shown in FIGS. 5 and 6. In FIGS. 5 and 6, each of members and portions which is functionally the same as that of the gas generator shown in FIG. 1 is designated with the same numeral, and a description thereof is omitted.

[0151] In a retainer 50 shown in FIG. 5, the axial end of the first combustion chamber 5 a is defined, and the axial average length of the first combustion chamber 5 a is adjusted. However, the retainer 50 does not divide the coolant means 22. Therefore, a working gas generated in the second combustion chamber 5 b flows into the flow-space 55 through the communication hole 10, the gas passes through the same coolant means 22 as the working gas generated in the first combustion chamber 5 a passes through, passes through the gap 25 to be discharged from the gas discharging port 26. In this case, even if the working gas is generated only in the first combustion chamber 5 a and the gas generating agent in the second combustion chamber 5 b is not yet ignited, the working gas generated in the first combustion chamber 5 a opens the gas discharging port 26 and therefore, the gas does not flow into the flow-space 55 through the coolant means 22 to rupture the seal tape 11 which closes the communication hole 10.

[0152] In FIG. 6, a retainer 50 defines the axial end of the first combustion chamber 5 a and adjusts the axial average length (L) of the first combustion chamber 5 a. And an outer wall end surface of the retainer 50 abuts against an inner wall surface of the diffuser shell 1 to separate flow-spaces for a working gas generated in the first combustion chamber 5 a and a working gas generated in the second combustion chamber 5 b from each other. Therefore, a working gas generated in the first combustion chamber 5 a is discharged from the gas discharging port 26 a, and a working gas generated in the second combustion chamber 5 b is discharged from the gas discharging port 26 b.

[0153] The air bag apparatus of the present invention using the above-described gas generator for the air bag comprises an actuation signal-outputting means including an impact sensor and a control unit, and a module case including the air bag gas generator 100 and an air bag. The air bag gas generator is connected to the actuation signal-outputting means (the impact sensor and the control unit) on the first and second igniters 23 a and 23 b side. In the air bag apparatus having such a structure, by appropriately setting an actuation signal outputting condition in the actuation signal outputting means, it is possible to adjust the gas generation amount in accordance with a degree of an impact and to adjust an expansion speed of the air bag. A structure of other than the gas generator in this air bag apparatus is comprehensible with reference of the one disclosed in JP-A No. 11-334517.

[0154] The gas generator for the air bag of the present invention will be explained based on the drawings showing a preferred embodiment.

[0155]FIG. 1 is a vertical sectional view showing one embodiment of the gas generator for the air bag of the invention.

[0156] The gas generator shown in this embodiment has two combustion chambers in the housing and two ignition means respectively corresponding to the combustion chambers. More specifically, the housing 3 formed by joining a diffuser shell 1 having a gas discharging port 26 and a closure shell 2 forming an inner accommodating space together with the diffuser shell 1. An inner cylindrical member 4 in a substantially cylindrical shape is disposed in the housing 3, and the outside thereof is the first combustion chamber 5 a. An interior of the inner cylindrical member 4 is divided into the two chambers by a partition wall 7, one of the chambers closer to the diffuser shell is a second combustion chamber 5 b, and the other chamber closer to the closure shell is an ignition means accommodating chamber 12. The partition wall 7 is engaged to a step-notched portion 6 formed in an inner surface of the inner cylindrical member 4.

[0157] Gas generating agents 9 a and 9 b are charged into the respective two combustion chambers 5 a and 5 b defined in the housing 3. The first gas generating agent 9 a is charged into the first combustion chamber 5 a, and the second gas generating agent 9 b is charged into the second combustion chamber 5 b. Each of the gas generating agents is ignited and burnt by actuation of the ignition means to generate a working gas for inflating an air bag. Shapes, compositions, composition ratios and amounts of the first and second gas generating agent 9 a and 9 b in the respective combustion chambers may be different from each other. Especially in this embodiment, the first gas generating agent 9 a is a gas generating agent including fuel and oxidizing agent. Guanidine derivatives or a mixture thereof is used as the fuel. Basic copper nitrate is used as the oxidizing agent. The same material as that of the first gas generating agent is used for the second gas generating agent 9 b as well.

[0158] A retainer 50 having an annular partition wall portion 52 is disposed on the axial end in the diffuser shell 1 side of the first combustion chamber 5 a. The partition wall portion 52 of the retainer 50 defines the axial length of the first combustion chamber 5 a and defines a flow-space for introducing a working gas generated due to combustion of the second gas generating agent to the coolant means. The retainer 50 comprises the cylindrical portion 51 disposed to face the inner cylindrical member at a predetermined distance and the annular partition wall portion 52 which is bent outwardly into a flange-like shape from the cylindrical portion 51. And further, an inwardly directed flange-like engaging portion 56 is formed opposite to the partition wall portion 52 on the cylindrical portion 51. An outer periphery of the inner cylindrical member is formed with a step-notched portion 53 formed by stepwisely notching the outer periphery in the closure shell 2 side to obtain a smaller diameter. The retainer 50 is disposed and fixed by engaging the engaging portion 56 to the step-notched portion 53. In the retainer 50 shown in FIG. 1, when the first gas generating agent is burnt at activation of the gas generator, the retainer 50 is pushed in a supporting direction by the step-notched portion 53 by the combustion pressure, and a fixed state and ignition state thereof become further reliable.

[0159] In the retainer 50 shown in this embodiment, since the cylindrical portion 51 is disposed to face the communication hole 10 without closing the same, a working gas which is generated by combustion of the second gas generating agent 9 b and discharged from the communication hole 10 once collides against the cylindrical portion 51. Therefore, if the second gas generating agent 9 b generates solid combustion products such as fluid or semi-fluid at the time of combustion, the combustion products collide against the cylindrical portion 51 and are removed from the working gas. As a result, when the gas generating agent generating such solid combustion products is used as the second gas generating agent 9 b, the solid combustion products are largely removed by the cylindrical portion 51, so that an amount of the later-described second coolant means 22 b and a thickness thereof in the radial direction can be reduced.

[0160] In the retainer 50, by adjusting the location thereof or the position of the partition wall portion 52, an inner shape, a capacity and the like of the first combustion chamber 5 a can be adjusted. Therefore, it is possible to adjust a ratio (D/L) of a radial average distance (D) of the combustion chamber 5 a to an axial average length (L) of the combustion chamber 5 a to be in the range of 0.2 to 2.0, preferably of 0.4 to 1.0 by adjusting the shape or position of the retainer 50, as shown in FIG. 1. In this embodiment, and end surface 2 of the first combustion chamber 5 a in the closure shell 2 side is defined by an inner surface of the closure shell 2, and the gas generating agent 9 a in the combustion chamber 5 a is supported by an underplate 54.

[0161] The retainer 50 shown in this embodiment defines a flow-space 55 on the opposite side to the first combustion chamber 5 a so that a working gas generated by combustion of the second gas generating agent 9 b passes through the flow-space. The flow-space 55 and the first combustion chamber are adjacent to each other in the radial direction of the housing via the retainer. In this case, the flow-space can be formed such as to go through the first combustion chamber. And the flow-space 55 and the second combustion chamber 5 b can communicate with each other through a communication hole 10 formed in a peripheral wall of the inner cylindrical member 4. In other words, the communication hole 10 is closed by the later-described seal tape 11, and the seal tape is ruptured by combustion of the second gas generating agent to make the flow-space 55 communicate with the second combustion chamber 5 b.

[0162] An ignition means including two igniters 23 a and 23 b, and a transfer charge 16 charged into an aluminum cup is accommodated in the ignition means accommodating chamber 12. The two igniters 23 a and 23 b are fixed to a collar assembly 31. The collar assembly 31 is fixed by crimping a lower end 4 a of the inner cylindrical member 4. The first igniter 23 a and the second igniter 23 b are accommodated in spaces defined by the partition wall 7 respectively. The transfer charge 16 is arranged above the first igniter 23 a in the space where the first igniter 23 a is accommodated.

[0163] Meanwhile, the space where the second igniter 23 b is accommodated is formed to communicate the second combustion chamber 5 b, the second combustion chamber 5 b can communicate a flow-space 55 defined by the retainer 50 through a communication hole 10 formed in the inner cylindrical member 4.

[0164] Working gases generated by combustion of the first gas generating agent 9 a and the second gas generating agent 9 b passes through annular coolant means 22 comprising laminated wire mesh or expanded metal to be discharged from a gas discharging port 26. Especially in this embodiment, the working gases generated from gas generating agents 9 a and 9 b pass through different coolant means 22 a and 22 b. More specifically, the first coolant means 22 a is disposed radially in the outside of the first combustion chamber 5 a, the second coolant means 22 b is disposed radially in the outside the second combustion chamber 5 b through the flow-space 55, and both the coolant means 22 a and 22 b are separated from each other by the retainer 50. In the gas generator shown in FIG.1, the first combustion chamber is formed to be adjacent to the inside of the first coolant means.

[0165] Therefore, in the gas generator shown in this embodiment, the transfer charge 16 is burnt by actuation of the first igniter 23 a, and its flame passes through the first flame-transferring port 17 a and is ejected into the first combustion chamber 5 a. Consequently, the first gas generating agent 9 a is ignited and burnt to generate a working gas, the working gas passes through the first coolant means 22 a, and reaches a gap 25 to be discharged from the gas discharging port 26. On the other hand, when the second igniter 23 b is actuated, its flame is ejected into the second combustion chamber 5 b to ignite and burn the second gas generating agent 9 b. A working gas generated by the combustion of the second gas generating agent 9 b proceeds to and passes through the flow-space 55 via the communication hole to reach the second coolant means 22 b. And the working gas is cooled and purified while passing through the second coolant 22 and passes through the gap 25 to be discharged from the gas discharging port 26. As described above, by arranging different flow-spaces or coolant means for the respective working gases generated in the combustion chambers, combustion of the gas generating agents in the respective combustion chambers can be adjusted easily, and thereby the operation output of the gas generator can be adjusted easily.

[0166] In the gas generator which is actuated as described above, even if the first gas generating agent is burnt, its flame is not ejected toward an exit (i.e., communication hole) of the second combustion chamber. Therefore, in selecting seal tapes for closing between the second combustion chamber and the flow-space, it is unnecessary to take influence by the combustion of the first gas generating agent into account. With this feature, for example, even aluminum seal tape using aluminum having lower melting point than that of stainless steel can be used.

[0167] Since the two coolant means 22 a and 22 b are separately disposed in the gas generator shown in this drawing, it is possible to adjust the purifying/cooling abilities of the coolant means 22 a and 22 b in accordance with the generation amounts of working gases generated in the combustion chambers 5 a and 5 b. If the working gas generated by combustion of the second gas generating agent 9 b is cooled by the second coolant means 22 b, an inner diameter of the first coolant means 22 a can be made larger. With this, the radial average distance (D) of the first combustion chamber 5 a can be increased.

[0168] In FIG. 1, a numeral 11 represents a seal tape for closing the communication hole 10, a numeral 18 represents a seal tape for closing the first flame-transferring port 17 a, and a numeral 27 represents a seal tape for closing the gas discharging port 26. The seal tapes are ruptured when flames or gases pass through the holes or ports.

[0169] In the gas generator shown in FIG. 1, working gases generated in the respective combustion chambers reach the filter means through different flow-paths, and the filter means is disposed in correspondence with each combustion chamber.

[0170] Such a gas generator can employ aspects shown in FIGS. 8(a) to (e) . That is, FIGS. 8(a) to (e) are sectional views of essential portions of aspects which can be carried out in the gas generator of the present invention. In FIG. 8, each of members and portions which is functionally the same as those of the gas generator shown in FIG. 1 is designated with the same numeral as that in FIG. 1, and a description thereof is omitted.

[0171] In a gas generator shown in FIG. 8(a), a retainer 50 defined the axial end of the first combustion chamber 5 a defines the flow-space 55. The annular second coolant means 22 b is disposed on the flow-space 55 side in the retainer 50. A working gas generated in the second combustion chamber is ejected from the through-hole 10 toward the flow-space 55, the working gas passes through the second coolant means 22 b and is ejected to the gap 25 from an opening 57 formed in the retainer 50, and finally reaches the gas discharging port 26. A retainer 50 used in the gas generator shown in FIG. 8(b) is the same as the retainer 50 shown in FIG. 8(a). However, the second coolant means 22 b is disposed in the vicinity of the through-hole 10. Therefore, the working gas ejected from the through-hole 10 first passes through the second coolant means 22 b, then passes through the flow-space 55 and is ejected to the gap 25 from the opening 57 formed in the retainer 50.

[0172] In a gas generator shown in FIG. 8(c), by using an annular retainer 50 having a hollow partition wall portion 52, the capacity of the first combustion chamber 5 a is increased, and at the same time, an amount of the second coolant means 22 b and a passing area of the working gas are obtained largely. In the gas generator shown in this drawing, a working gas generated in the second combustion chamber 5 b is ejected from the through-hole 10, and passes through the flow-space 55 to reach the second coolant means 22 b.

[0173] In a gas generator shown in FIG. 8(d), a cover shell 1 b is provided outside the diffuser shell 1 a, and a gap serving as the flow-space 55 is formed therebetween. A working gas generated in the second combustion chamber 5 b is ejected from an opening 59 of a ceiling (upper side in the drawing) of the diffuser shell 1 a into the gap between the diffuser shell 1 a and the cover shell 1 b, passes through the second coolant means 22 b and then through the flow-space 55 to reach the first coolant means 22 a from an opening 60 formed just above the first coolant means 22 a.

[0174] In a gas generator shown in FIG. 8(e), an end of the inner cylindrical member 4 in the diffuser shell 1 side is formed into a substantially outwardly directed flange-like shape, and the through-hole 10 is provided in the flange-like portion. The retainer 50 engages the flange-like portion to form the flow-space 55. The second coolant means 22 b is disposed on the flange-like portion in the second combustion chamber 5 b side. In the gas generator shown in this drawing, a working gas generated in the second combustion chamber passes through the second coolant means 22 b and then is ejected from the through-hole 10 of the inner cylindrical member 4, and passes through the flow-space 55 to reach the gas discharging port 26.

[0175] As another embodiment, the present invention also provides a gas generator in which flow-paths of working gases generated in the respective combustion chambers are made differently from each other, the working gases pass through a single coolant means. That is, in this gas generator, working gases generated in the respective combustion chambers pass through the same coolant means. In this gas generator of this aspect, the combustion chambers are spatially connected to each other only through the coolant means. This gas generator can employ aspects shown in FIGS. 9(a) to (e) . In FIG. 9, each of members and portions which is functionally the same as that of the gas generator shown in FIG. 1 is designated with the same numeral, and a description thereof is omitted.

[0176] In a gas generator shown in FIG. 9(a), a coolant means 22 is disposed adjacent to the first combustion chamber 5 a in the axial direction, a space where the coolant means 22 is disposed is practically partitioned from the first combustion chamber 5 a by the retainer 50. In the gas generator shown in this drawing, a working gas generated in the second combustion chamber 5 b passes through the coolant means 22 and is discharged from the gas discharging port 26. Therefore, the working gas never flows into the first combustion chamber 5 a. A working gas generated in the first combustion chamber 5 a flows into a space where the coolant means 22 is positioned from a gap between an inner edge of the retainer 50 and the inner cylindrical member 4, and then passes through the coolant means and is discharged from the gas discharging port 26.

[0177] In a gas generator shown in FIG. 9(b), a working gas generated in the second combustion chamber 5 b passes through the through-hole 10 of the inner cylindrical member 4 and reaches the flow-space 55, passes through this space and is ejected into the coolant means 22 from the opening 57 formed in the retainer 50. A working gas flowing into the coolant means 22 passes through the gap 25 and is discharged from the gas discharging port 26, so that the gas never flows into the first combustion chamber 5 a.

[0178] In a gas generator shown in FIG. 9(c), an annular retainer 50 having a hollow partition wall portion 52 is used, the capacity of the first combustion chamber 5 a is increased, and at the same time, an amount of the second coolant means 22 b and a passing area of the working gas are obtained largely. In the gas generator shown in this drawing, a working gas generated in the second combustion chamber 5 b is ejected from the through-hole 10 into the flow-space 55, passes through the flow-space 55 to reach the coolant means 22, and further passes through the coolant means 22 to reach the gap 25 and finally is discharged from the gas discharging port 26. That is, a working gas generated in the second combustion chamber 5 b flows toward the gas discharging port 26, so that the gas never flows into the first combustion chamber 5 a through the coolant means 22.

[0179] In a gas generator shown in FIG. 9(d), an inner cylindrical member 4 in which its portion near the through-hole 10 swells to contact with an inner periphery of the coolant means 22 is used. Therefore, a working gas generated in the second combustion chamber 5 b passes through the through-hole 10 of the inner cylindrical member 4 and is directly ejected into the coolant means 22, and flows through the coolant means 22 toward the gas discharging port 26. Thus, a working gas generated in the second combustion chamber 5 b never passes through the coolant means 22 nor flows into the first combustion chamber 5 a.

[0180] In a gas generator shown in FIG. 9(e), a cover shell 1 b is provided outside the diffuser shell 1 a, and a flow-space 55 is formed therebetween. A working gas generated in the second combustion chamber 5 b is ejected from an opening 59 of a ceiling of the diffuser shell 1 a into the flow-space 55, passes through the flow-space 55, is ejected into the coolant means 22 from an opening 60 provided just above the coolant means 22 in the diffuser shell 1 b, and flows through the coolant means 22 toward the gas discharging port 26. Thus, a working gas generated in the second combustion chamber 5 b never passes through the coolant means 22 nor flows into the first combustion chamber 5 a.

[0181] As another embodiment, the present invention also provides a gas generator in which flow-paths of working gases generated in the combustion chambers are different from each other, the gases are introduced to different coolant means and discharged from different gas discharging ports. In such a gas generator, it is necessary to form different gas discharging ports 26 a and 26 b for the respective combustion chambers 5 a and 5 b, but the gas discharging ports do not necessarily have to be formed in a peripheral surface of the cylindrical housing. Such a gas generator can employ aspects shown in FIGS. 10(a) to (d). In FIG. 10, each of members and portions which is functionally the same as that of the gas generator shown in FIG. 1 is designated with the same numeral, and a description thereof is omitted.

[0182] In a gas generator shown in FIG. 10(a), a second gas discharging port 26 a is formed on a ceiling side of the diffuser shell 1, and a second coolant means 22 b is disposed in the diffuser shell 1 side in the second combustion chamber 5 b. A working gas generated in the first combustion chamber 5 a passes through a first coolant means 4 a and is discharged from a first gas discharging port 26 a. A working gas generated in the second combustion chamber 5 b passes through the second coolant means 22 b and is discharged from a second gas discharging port 26 b. Thus, in this gas generator, the working gases generated in the respective combustion chambers are not mixed with each other in the housing, nor the working gas generated in one of the combustion chambers does not flow into the other combustion chamber.

[0183] In a gas generator shown in FIG. 10(b) also, like the gas generator shown in FIG. 10(a), the second gas discharging port 26 b is provided on the ceiling side of the diffuser shell 1, and the second coolant means 22 b is provided in the second combustion chamber 5 b in the diffuser shell 1 side. Especially in the gas generator shown in this drawing, a center portion of the ceiling of the diffuser shell 1 projects in the axial direction, and the second gas discharging port 26 b is provided in the projected peripheral surface. Therefore, in this gas generator also, working gases generated in the respective combustion chambers are not mixed with each other in the housing, nor a working gas generated in one of the combustion chambers does not flow into the other combustion chamber.

[0184] In a gas generator shown in FIG. 10 (c), a cover shell 1 b is provided outside the diffuser shell 1 a, and a flow-space 55 is formed therebetween. In this gas generator shown in this drawing, the cover shell 1 b constitutes the housing together with the diffuser shell 1 a and the closure shell 2. Especially, this cover shell 1 b is formed into a cylindrical shape with a bottom and is provided at its peripheral surface with a second gas discharging port 26 b. As a result, a working gas generated in the second combustion chamber 5 b is ejected from an opening 59 in the ceiling side of the diffuser shell, passes through the second coolant means 22 b and then through the flow-space 55, and is discharged from the second gas discharging port out of the housing. Therefore, the working gases generated in the respective combustion chambers are not mixed with each other in the housing, nor the working gas generated in one of the combustion chambers does not flow into the other combustion chamber.

[0185] In a gas generator shown in FIG. 10(d), an inner cylindrical member 4 is provided to go through a ceiling of the diffuser shell 1 a, and an opening end of the inner cylindrical member 4 is closed with a cover shell 1 b which is integrally formed together with the diffuser shell 1 a. Thus, in the gas generator shown in this drawing also, the cover shell 1 b constitutes the housing together with the diffuser shell 1 a and the closure shell 2. In this gas generator, the axial direction of the first combustion chamber 5 a is defined by an inner surface of the ceiling of the diffuser shell 1 a, and the flow-space 55 is formed between the diffuser shell 1 a and the cover shell 1 b. The second coolant means is provided inside the cover shell 1 b. In this gas generator, a working gas generated in the second combustion chamber 5 b flows into the flow-space 55 from the through-hole formed in the inner cylindrical member 4, passes through the second coolant means 22 b, and is discharged out of the housing from the second gas discharging port 26 b. Thus, in the gas generator shown in this drawing also, the working gases generated in the respective combustion chambers are not mixed with each other in the housing, nor the working gas generated in one of the combustion chambers does not flow into the other combustion chamber.

[0186] Such a gas generator can employ aspects shown in FIGS. 5 and 6. In FIGS. 5 and 6, each of members and portions which is functionally the same as that of the gas generator shown in FIG. 1 is designated with the same numeral, and a description thereof is omitted.

[0187] In a retainer 50 shown in FIG. 5, the axial end of the first combustion chamber 5 a is defined, and the axial average length of the first combustion chamber 5 a is adjusted. However, the retainer 50 does not divide the coolant means 22. Therefore, a working gas generated in the second combustion chamber 5 b flows into the flow-space 55 through the communication hole 10, the gas passes through the same coolant means 22 as the working gas generated in the first combustion chamber 5 a passes through, and then passes through the gap 25 to be discharged from the gas discharging port 26. In this case, even if the working gas is generated only in the first combustion chamber 5 a and the gas generating agent in the second combustion chamber 5 b is not yet ignited, the working gas generated in the first combustion chamber 5 a opens the gas discharging port 26 and therefore, the gas does not flow into the flow-space 55 through the coolant means 22 to rupture the seal tape 11 which closes the communication hole 10.

[0188] In FIG. 6, a retainer 50 defines the axial end of the first combustion chamber 5 a and adjusts the axial average length (L) of the first combustion chamber 5 a. And an outer wall end surface of the retainer 50 abuts against an inner wall surface of the diffuser shell 1 to separate flow-spaces for a working gas generated in the first combustion chamber 5 a and a working gas generated in the second combustion chamber 5 b from each other. Therefore, a working gas generated in the first combustion chamber 5 a is discharged from the gas discharging port 26 a, and a working gas generated in the second combustion chamber 5 b is discharged from the gas discharging port 26 b.

[0189]FIG. 11 shows a gas generator characterized in an engaged portion between the inner cylindrical member and the retainer. That is, in the gas generator shown in this drawing, a cylindrical portion (or inner cylindrical portion) 51 of the retainer 50 is provided with a swelling portion 63 having part thereof swelled outwardly in the radial direction, and an O-ring 64 is disposed between the swelling portion 63 and the inner cylindrical member. With this structure, the O-ring 64 seals between the inner cylindrical member 4 and the retainer 50 (especially swelling portion 63), and even if the first gas generating agent 9 a is burnt, a working gas does not flow into the flow-space (or flow-path) 55. When the first gas generating agent 9 a and the second gas generating agent 9 b are burnt simultaneously, a pressure inside the first combustion chamber 5 a is sufficiently increased by combustion of the first gas generating agent 9 a and thus, a working gas generated in the second combustion chamber 9 b does not flow into the first combustion chamber 5 a. Therefore, when the engagement structure between the inner cylindrical member and the retainer is formed as shown in FIG. 11, it is unnecessary to adjust the size of the cylindrical portion (or inner cylindrical portion) 51 of the retainer 50 to fit outwardly the inner cylindrical member 50, and a gap may be disposed therebetween.

[0190] Especially when the engagement structure between the inner cylindrical member and the retainer is formed as shown in FIG. 11, the retainer 50 is supported by the second coolant means 22 b, and thereby, the retainer 50 is prevented from moving in the axial direction of the housing. And, the cutting process of the outer peripheral surface of the inner cylindrical member (i.e., outer peripheral surface of the cylindrical peripheral wall) can be eliminated, so that it is advantageous to manufacturing and costs.

[0191] Concerning the engagement structure between the inner cylindrical member and the retainer, in the gas generator shown in FIG. 1, the engaging portion 56 provided on an end of the cylindrical portion (or inner cylindrical portion) 51 is engaged to the step-notch 53 of the inner cylindrical member, thereby disposing and fixing the retainer 50 in the housing, and in the gas generator shown in FIGS. 8(a) to (d) and (f), part of the cylindrical portion 51 is formed into such a size to be fitted outwardly to the cylindrical peripheral wall of the inner cylindrical member 4, the retainer 50 is press-fitted outside the inner cylindrical member, and the retainer 50 is disposed and fixed in the housing.

[0192] In FIG. 11, each of members and portions which is functionally the same as that of the gas generator shown in FIG. 1 is designated with the same numeral, and a description thereof is omitted.

[0193] The air bag apparatus of the present invention using the above-described gas generator for the air bag comprises an actuation signal-outputting means including an impact sensor and a control unit, and a module case including the air bag gas generator 100 and an air bag. The air bag gas generator is connected to the actuation signal-outputting means (the impact sensor and the control unit) on the first and second igniters 23 a and 23 b side. In the air bag apparatus having such a structure, by appropriately setting an actuation signal outputting condition in the actuation signal outputting means, it is possible to adjust the gas generation amount in accordance with a degree of an impact and to adjust an expansion speed of the air bag. A structure of other than the gas generator in this air bag apparatus is comprehensible with reference of the one disclosed in JP-A No. 11-334517. 

1. A gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member disposed to define an inner space of the housing, an ignition means disposed inside the inner cylindrical member, and a first combustion chamber provided radially in the outside of the inner cylindrical member to accommodate a gas generating agent, wherein, the first combustion chamber is adjusted such that a ratio (D/L) of its radial average distance (D)to its axial average length (L) is in the range of 0.2 to 2.0.
 2. A gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member disposed to define an inner space of the housing, an ignition means disposed inside the inner cylindrical member, and a first combustion chamber provided radially in the outside of the inner cylindrical member to accommodate a gas generating agent, wherein, a retainer provided with a partition wall surface is disposed on an axial end of said first combustion chamber, and said partition wall surface limits an axial length of the first combustion chamber.
 3. A gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member disposed to define an inner space of the housing, an ignition means disposed inside the inner cylindrical member, and a first combustion chamber provided radially in the outside of the inner cylindrical member to accommodate a gas generating agent, wherein, said housing limits an axial length of said first combustion chamber with an inner surface existing in the axial direction of the first combustion chamber.
 4. A gas generator for an air bag comprising, in a cylindrical housing comprising a diffuser shell which has a cylindrical shape with a top and has a gas discharging port, and a closure shell which has a cylindrical shape with a bottom and forms an inner space together with the diffuser shell, an inner cylindrical member disposed to define the inner space of the housing, an ignition means disposed inside the inner cylindrical member, and a first combustion chamber accommodating a gas generating agent provided radially in the outside of the inner cylindrical member, wherein said inner cylindrical member is provided with a flame-transferring port for ejecting flames generated by actuation of the ignition means into the first combustion chamber, and the flame-transferring port is formed such that a distance L₁ from the center of the axial average length measured from the closure shell-inner bottom surface in the first combustion chamber to the center of the flame-transferring port is not more than ¼ of the axial average length L in the first combustion chamber.
 5. A gas generator for an air bag according to claim 1 or 3, wherein a retainer provided with a partition wall surface is disposed on an axial end of said first combustion chamber, and said partition wall surface limits the axial length of the first combustion chamber.
 6. A gas generator for an air bag according to claim 1 or 4, wherein the housing limits an axial length of the first combustion chamber with an inner surface existing on the axial direction of the first combustion chamber.
 7. A gas generator for an air bag according to any one of claims 1 to 6, wherein the inner cylindrical member is provided with a flame-transferring port for ejecting flames generated by actuation of the ignition means into the first combustion chamber, and the flame-transferring port is formed such that a distance L₁ from the center of the axial average length in the first combustion chamber to the center of the flame-transferring port is not more than ¼ of the axial average length L in the first combustion chamber.
 8. A gas generator for an air bag according to any one of claims 1 to 7, wherein the first combustion chamber is formed annularly.
 9. A gas generator for an air bag according to any one of claims 1 to 8, wherein the inside of the inner cylindrical member is further divided into an ignition means accommodating chamber and a second combustion chamber by a partition wall.
 10. A gas generator for an air bag according to claim 9, wherein a gas generated by combustion of the gas generating agent accommodated in the second combustion chamber is not directly ejected into the first combustion chamber.
 11. A gas generator for an air bag according to claim 9 or 10, wherein the retainer limits the axial average length of the first combustion chamber and defines a flow-space of a gas oppositely to the first combustion chamber, and the inner cylindrical member is formed with a communication hole capable of making the second combustion chamber and the flow-space of gas communicate with each other.
 12. A gas generator for an air bag according to any one of claims 1 to 11, wherein the gas generating agent accommodated in the first combustion chamber includes fuel and oxidizing agent, and the oxidizing agent is basic metal nitrate.
 13. A gas generator for an air bag according to claim 12, wherein the fuel is guanidine derivatives or a mixture thereof.
 14. A retainer used for a gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall provided with a through-hole, and at least either of an ignition means and a gas generating agent is disposed inside the inner cylindrical member, wherein the retainer includes a cylindrical portion which is positioned with a distance from an outer peripheral surface of the cylindrical peripheral wall and faces the outer peripheral surface, and a flange-shaped partition wall portion integrally formed together with the cylindrical portion, and at least either of the cylindrical portion and the partition wall portion changes a flow of a gas ejected from the through-hole formed in the cylindrical peripheral wall and collects combustion products other than gaseous material included in the gas.
 15. A retainer according to claim 14, wherein the cylindrical portion is formed into a size and shape capable of covering at least a communication hole of the inner cylindrical member.
 16. A retainer according to claim 14 or 15, wherein part of the cylindrical portion is formed into a size and shape capable of fitting outwardly the cylindrical peripheral wall of the inner cylindrical member.
 17. A retainer according to any one of claims 14 to 16 used for a gas generator for an air bag which accommodates annular coolant means for purifying or cooling a gas generated by combustion of a gas generating agent stored in a housing, wherein all or part of the cylindrical portion is formed into a shape and size capable of fitting to at least one of an inner peripheral surface and an outer peripheral surface of the coolant means and an inner peripheral surface of a housing peripheral wall.
 18. A retainer according to any one of claims 14 to 17, wherein an end opening of the cylindrical portion is integrally formed with a engaging portion which engages a cylindrical peripheral wall of an inner cylindrical member in an inwardly directed flange-like shape.
 19. A retainer according to any one of claims 14 to 18 used for a gas generator for an air bag in which a first combustion chamber for accommodating the gas generating agent is provided radially in the outside of the inner cylindrical member wherein, the partition wall portion is formed into a shape and size capable of defining at least an axial end of the first combustion chamber.
 20. A gas generator for an air bag comprising, in a cylindrical housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall provided with a through-hole, at least either of an ignition means and a gas generating agent disposed in the inner cylindrical member, and a retainer, which has a cylindrical portion surrounding part of the inner cylindrical member and a flange-shaped partition wall portion integrally formed on the cylindrical portion, disposed outside the inner cylindrical member, wherein a cylindrical portion of the retainer is positioned with a distance from an outer peripheral surface of the cylindrical peripheral wall and faces the outer peripheral surface, and at least one of the cylindrical portion and the peripheral wall changes flow of a gas ejected from a through-hole formed in the cylindrical peripheral wall of the inner cylindrical member and collects combustion products other than gaseous material included in the gas.
 21. A gas generator for an air bag according to claim 20, wherein the cylindrical portion of the retainer exists at a horizontally projected position of a through-hole provided on cylindrical peripheral wall of the inner cylindrical member.
 22. A gas generator for an air bag according to claim 20 or 21, wherein the cylindrical portion of the retainer faces the communication hole of the inner cylindrical member without closing the communication hole.
 23. A gas generator for an air bag according to any one of claims 20 to 22, wherein part of the cylindrical portion of the retainer is fitted outwardly to the cylindrical peripheral wall of the inner cylindrical member.
 24. A gas generator for an air bag according to any one of claims 20 to 23, wherein an annular coolant means for purifying or cooling a gas generated by combustion of the gas generating agent stored in the housing is accommodated in the housing, and all or part of the cylindrical portion of the retainer is fitted to at least one of an inner peripheral surface and an outer peripheral surface of the coolant means and an inner peripheral surface of a housing peripheral wall.
 25. A gas generator for an air bag according to any one of claims 20 to 24, wherein an end opening of the cylindrical portion is integrally formed with a engaging portion which engages a cylindrical peripheral wall of an inner cylindrical member in an inwardly directed flange-like shape.
 26. A gas generator for an air bag according to claim 25, wherein the housing comprises a diffuser shell having a gas discharging port and a closure shell forming an inner space together with the diffuser shell, the inner cylindrical member includes a step-notch formed by stepwisely notching an outer peripheral surface of the inner cylindrical member in the closure shell side, and a engaging portion of the retainer engages the notch.
 27. A gas generator for an air bag according to any one of claims 20 to 26, wherein a first combustion chamber for accommodating the gas generating agent is provided radially in the outside of the inner cylindrical member, and a peripheral wall of the retainer is formed into a shape and size capable of defining at least an axial end of the first combustion chamber and is provided on the axial end of the first combustion chamber.
 28. A gas generator for an air bag according to claim 27, wherein, in the retainer, the partition wall portion receives combustion pressure of the first gas generating agent accommodated in the first combustion chamber, and thereby the engaging portion is pushed against a step-notched portion of the inner cylindrical member.
 29. A gas generator for an air bag according to any one of claims 20 to 28, wherein, inside the inner cylindrical member, an ignition means accommodating chamber and a second combustion chamber are defined adjacent to each other in the axial direction by a partition wall, and a communication hole of the inner cylindrical member is open at the second combustion chamber.
 30. A gas generator for an air bag according to any one of claims 20 to 29, wherein the inside the inner cylindrical member is further divided into an ignition means accommodating chamber and a second combustion chamber by a partition wall, and the retainer collects combustion products other than gaseous material generated by combustion of the second gas generating agent.
 31. A gas generator for an air bag according to any one of claims 20 to 30, wherein the gas generating agent accommodated in the first combustion chamber includes fuel and oxidizing agent, the oxidizing agent is basic metal nitrate.
 32. A gas generator for an air bag according to claim 31, wherein the fuel is guanidine derivatives or a mixture thereof.
 33. A gas generator for an air bag comprising, in a housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall, two combustion chambers defined by the inner cylindrical member, wherein gas generating agents to be burnt for generating a working gas are charged in the respective combustion chambers, and working gases generated in the respective combustion chambers pass through different flow-paths and reach the gas discharging port.
 34. A gas generator for an air bag comprising, in a housing having a gas discharging port, an inner cylindrical member having a cylindrical peripheral wall and two combustion chambers defined by the inner cylindrical member, wherein gas generating agents to be burnt for generating a working gas are charged in the respective combustion chambers, and a working gas generated in one of the combustion chambers reaches the gas discharging port without passing through the other combustion chamber.
 35. A gas generator for an air bag according to claim 33 or 34, which further comprises an ignition means to ignite a gas generating agent, and the ignition means is accommodated inside the inner cylindrical member.
 36. A gas generator for an air bag according to any one of claims 33 to 35, wherein a working gas generated in one of the combustion chambers passes through a flow-space divided from the other combustion chamber and does not pass through the other combustion chamber.
 37. A gas generator for an air bag according to any one of claims 33 to 36, wherein working gases generated in the respective combustion chambers pass through different coolant means to reach the gas discharging port.
 38. A gas generator for an air bag according to any one of claims 33 to 37, wherein working gases generated in the respective combustion chambers reach different gas discharging ports respectively provided in the corresponding combustion chambers.
 39. A gas generator for an air bag according to any one of claims 33 to 38, wherein one or both of the gas discharging port and coolant means are provided independently of each other, in correspondence with each combustion chambers defined in the housing.
 40. A gas generator for an air bag according to any one of claims 33 to 39, wherein all or part of one of the two combustion chambers is defined in the housing by being surrounded by the other combustion chamber.
 41. A gas generator for an air bag according to any one of claims 33 to 40, wherein the coolant means is formed cylindrically, and either or both of the two combustion chambers are adjacent to the inside of the coolant means.
 42. A gas generator for an air bag according to any one of claims 33 to 41, wherein a working gas generated in one of the two combustion chambers passes through a flow-space which can communicate with said combustion chamber to reach the gas discharging port.
 43. A gas generator for an air bag according to any one of claims 33 to 42, wherein a working gas generated in one of the two combustion chambers passes through a flow-space which can communicate with said combustion chamber to reach the gas discharging port, and the flow-space is defined in the housing to pass through the other combustion chamber or to be adjacent to the other combustion chamber.
 44. A gas generator for an air bag according to any one of claims 36, 42 and 43, wherein the flow-space communicating with one of the two combustion chambers is defined in the housing by the retainer defining an end of the other combustion chamber.
 45. A gas generator for an air bag according to any one of claims 42 to 44, wherein a seal tape closes between the flow-space and the combustion chamber which can communicate with the flow-space, and the seal tape is ruptured only by pressure of the combustion chamber which can communicate with the flow-space.
 46. A gas generator for an air bag according to any one of claims 42 to 45, wherein one of the two combustion chambers and the flow-path can communicate with each other through the communication hole, and the communication hole is sealed by a seal tape, and the seal tape is provided in a position where combustion flames of the gas generating agent accommodated in the other combustion chamber does not touch the seal tape.
 47. A gas generator for an air bag according to claim 46, wherein the seal tape is made of aluminum and having a metal layer thickness of 10 to 100 mm.
 48. A gas generator for an air bag according to any one of claims 33 to 47, wherein one of the two combustion chambers is provided inside the inner cylindrical member disposed in the gas generator, and the other combustion chamber is provided radially in the outside of the inner cylindrical member.
 49. A gas generator for an air bag according to claim 48, wherein the combustion chamber defined inside the inner cylindrical member and the other combustion chamber are provided concentrically to be adjacent in the radial direction.
 50. A gas generator for an air bag according to any one of claims 33 to 49, wherein an interior of the inner cylindrical member is divided into two chambers which are adjacent to each other in the axial direction by a partition wall which expands radially, one of the two chambers defined inside the inner cylindrical member closer to the gas discharging port is a combustion chamber, and the other chamber is an ignition means accommodating chamber for accommodating the ignition means.
 51. An air bag apparatus comprising: a gas generator for an air bag, an impact sensor for detecting an impact to actuate the gas generator, the air bag which introduces gas generated in the gas generator to expand, and a module case for accommodating the air bag, wherein the gas generator for the air bag is the one in any one of claims 1 to
 50. 